Field of the Invention
The present invention relates to an image capturing system, an image capturing apparatus, a control method, and a recording medium, and particularly to correction processing that is performed by applying a predetermined filter to an image capturing signal.
Description of the Related Art
In an image capturing apparatus such as a digital camera, various correction processes are applied to an image signal obtained by capturing. One of the correction processes to be applied is recovery processing of applying a recovery filter based on an optical transfer function (OTF) unique to an imaging optical system to reduce the influence, on the image signal, of aberration or diffraction arising from the characteristic of the imaging optical system (Japanese Patent Laid-Open No. 2011-217087).
The influence of aberration or diffraction on the image signal changes depending on the optical transfer function of a mounted imaging optical system as in a lens interchangeable camera. In addition, the influence changes depending on even capturing conditions such as the focal distance, aperture value, and subject distance that were set at the time of capturing, and the image height position. To obtain a satisfactory correction effect, a different recovery filter is required in accordance with a combination of the optical transfer function of a selected imaging optical system, capturing conditions, and an image height position.
However, the data amount of a high-accuracy recovery filter tends to increase, and a large storage capacity is necessary to hold recovery filters corresponding to various conditions in the storage area. This is sometimes not practical in terms of the circuit scale.
Unlike this, there is a method of storing OTF coefficients smaller in data amount than the recovery filter for a plurality of capturing conditions, and applying interpolation, FFT, or the like to an OTF coefficient corresponding to finalized capturing conditions, thereby generating a recovery filter.
However, recovery filter generation processing requires a heavy computational load and takes time. When performing recovery processing on an image signal at the time of capturing, the next capturing cannot be performed before the completion of processing. Conventionally, when the user selects an image, it is necessary to generate a recovery filter and execute recovery processing cumbersomely.